Aircraft fuel types explained: Jet A, Jet A-1, avgas and approved alternatives, including what airliners, piston aircraft and prop planes use.
Aircraft use fuel matched to their engine and approved specifications. Turbine aeroplanes—including jets, turboprops and most turbine helicopters—normally burn kerosene-based Jet A or Jet A-1. Most spark-ignition piston aircraft use aviation gasoline, commonly 100LL, while some approved compression-ignition piston engines also use Jet A or Jet A-1.
For our Aviation & Real-World Flying readers, the quickest reliable rule is to identify the engine, not the aircraft’s size or whether it has a propeller. There is no single fuel used in every aeroplane, and apparently similar aircraft can require different grades after an engine conversion.
Which fuel is used in an aircraft?
The correct aircraft fuel type is determined by the engine, airframe approvals and operating limitations.
| Aircraft or engine type | Typical fuel | What matters |
|---|---|---|
| Airliner or business-jet turbine | Jet A or Jet A-1 | Kerosene-type turbine fuel approved for the aircraft |
| Turboprop or turbine helicopter | Jet A or Jet A-1 | A propeller or rotor does not mean the aircraft uses avgas |
| Spark-ignition piston engine | Usually 100LL avgas; approved unleaded avgas or automotive petrol in some installations | The exact fuel grade must be approved for both engine and airframe |
| Compression-ignition piston engine | Usually Jet A or Jet A-1 | Often called an aviation diesel, despite commonly using aviation turbine fuel |
| Military turbine aircraft | JP-5, JP-8 or another specified military fuel | Additives and operating specifications differ from civil grades |
| Purpose-built electric or hydrogen aircraft | Electricity or hydrogen | These require dedicated propulsion and storage systems |
The aircraft flight manual, pilot’s operating handbook, cockpit placards and approved supplements are authoritative. Aircraft appearance is not: the same basic airframe may exist with an avgas piston engine, a Jet A-burning compression-ignition conversion or a turboprop engine.
What are the main types of jet fuel?
Jet A and Jet A-1 are the principal civil jet fuels used by airliners, business jets, turboprops and turbine helicopters.
- Jet A is used mainly in the United States. Its specification sets a maximum freezing point of −40°C.
- Jet A-1 is the usual international grade. Its lower maximum freezing point of −47°C suits cold, high-altitude and long-range operations.
- Jet B is a more volatile, wide-cut fuel used only in limited very-cold-weather operations. Its handling characteristics prevent it from being a routine substitute for Jet A or Jet A-1.
- JP-5 and JP-8 are military turbine fuels with specified properties and additive packages. They must not be treated as automatically interchangeable with civil fuel.
Jet fuel is often described as aviation kerosene, but ordinary heating kerosene and road diesel are not approved substitutes. Fuel specifications control characteristics such as freezing point, flash point, contamination limits and additives—not merely whether the liquid will burn.
What fuel do commercial aircraft use?
Commercial jet aircraft normally use Jet A or Jet A-1, subject to the grades listed in the aircraft and operator documentation.
Fuel is delivered by volume but airline planning and cockpit indications usually work in kilograms or pounds. Density changes with temperature and fuel batch, so the same number of litres does not always have the same mass. Our explanation of why aviation calculations use fuel mass rather than volume covers the operational reason for that distinction.
Is sustainable aviation fuel a different type of jet fuel?
Sustainable aviation fuel, or SAF, is a production and sourcing category rather than permission to use any bio-derived liquid in a turbine engine.
Approved SAF pathways commonly produce a synthetic blending component which is combined with conventional fuel and released under an applicable aviation-fuel specification. Permitted blend proportions depend on the production pathway and approval. Once certified as a finished drop-in fuel, the blend is handled as Jet A or Jet A-1; raw vegetable oil and unapproved biofuel are not substitutes.
SAF can reduce lifecycle greenhouse-gas emissions depending on its feedstock and production process, but it does not eliminate exhaust emissions. Hydrogen and battery power are separate propulsion technologies requiring purpose-designed aircraft and infrastructure.
What kind of fuel do prop planes use?
Propeller planes may use avgas, Jet A, Jet A-1, approved automotive petrol or electricity; the propeller alone does not identify the fuel.
- Traditional light piston aircraft commonly use 100LL avgas.
- Compression-ignition piston aircraft commonly use Jet A or Jet A-1.
- Turboprops use approved turbine fuel, normally Jet A or Jet A-1.
- Some light aircraft can use unleaded avgas or automotive petrol only under a specific approval.
- Electric aircraft use stored electrical energy to turn the propeller.
100LL is normally dyed blue and contains tetraethyl lead. “LL” means low lead compared with older aviation grades, not lead-free. Its aviation performance rating is also not directly equivalent to the RON or AKI octane number shown on a roadside petrol pump.
Automotive petrol, known as mogas in aviation, is acceptable only when the engine and airframe approval allows the required octane rating, vapour pressure, ethanol content and other properties. This is why ordinary car petrol is not a universal substitute for avgas.
Do propeller planes use jet fuel?
Yes. Every conventional turboprop uses a gas turbine to turn its propeller through a reduction gearbox, so it burns an approved jet or turbine fuel rather than avgas.
Some propeller-driven piston aircraft also use Jet A or Jet A-1 because they have compression-ignition engines. Our comparison of compression-ignition and avgas aircraft engines explains why both can drive a propeller while requiring different fuels.
Are jet fuel and avgas interchangeable?
No. Jet fuel and avgas are not interchangeable unless the aircraft’s approved documentation expressly permits the alternative grade.
- Jet fuel in a spark-ignition avgas engine can cause detonation, power loss and engine failure because it lacks the required anti-knock performance.
- Avgas in a turbine engine can breach operating limits and leave harmful lead deposits. A small number of turbine manuals permit restricted emergency use, but that is not general approval.
- Unapproved automotive petrol can introduce vapour-lock, ethanol-compatibility and octane problems.
- Road diesel or domestic kerosene does not become acceptable merely because it resembles an approved aviation fuel.
A mistake we see repeatedly is relying on colour or nozzle shape as proof. 100LL is normally blue, while clean jet fuel is generally clear to pale straw-coloured, but dye can fade and mixed or contaminated fuel may look plausible. Misfuelling-prevention nozzles, pump labels and verbal assurances are safeguards, not replacements for checking the specified grade.
How do pilots confirm the correct aircraft fuel?
Pilots identify the approved grade from the aircraft documentation and verify that the delivered fuel matches the order before flight.
- Read the limitations: check the flight manual or pilot’s operating handbook, fuel placards and any approved engine-conversion or fuel-system supplement.
- Order the complete grade: specify Jet A, Jet A-1, 100LL or the exact approved alternative rather than asking vaguely for “jet fuel” or “avgas”.
- Check the source: compare the bowser or pump label, delivery documentation and requested quantity with the order.
- Sample as required: follow the approved pre-flight procedure for checking drains and sumps for water, sediment, mixed fuel and other contamination. A normal-looking sample cannot prove the grade by itself.
- Stop when uncertain: do not start or fly the aircraft if misfuelling is suspected. The fuel must be identified and any contamination addressed by qualified personnel.
Is reserve fuel a separate fuel type?
Reserve, usable and unusable fuel describe quantities, not different grades of fuel.
Usable fuel is the amount available to the engines under the defined operating conditions. Unusable fuel remains trapped or unavailable, while reserve is a planning allowance intended to remain after the planned flight. The distinctions are covered in our guide to total, usable, unusable and reserve fuel quantities.
Does fuel type matter in flight simulators?
Fuel type matters in a flight simulator only when the selected aircraft models fuel grade or its effects; most aircraft simply assume that the loaded fuel is the approved type.
Detailed add-ons may model fuel density, temperature, tank transfer, imbalance, boost pumps and centre-of-gravity changes. In simpler aircraft, the fuel menu normally controls quantity rather than allowing a choice between avgas and Jet A.
If a simulated engine will not start, changing the supposed fuel grade is rarely the fix. Check the tank selector, fuel shut-off valve, mixture or condition lever, boost pumps, ignition and available electrical or pneumatic starting power. Also check the units: entering gallons where kilograms or pounds are expected can produce a serious fuel shortfall even though the displayed number looks reasonable.
Use the checklist supplied for the specific simulated aircraft because piston, turboprop and jet start logic differs. Simulator behaviour must never be used to determine the correct fuel or procedure for a real aircraft.